Comprehensive Analysis and Key Factor Exploration of the Impact of Straw Returning on Soil Organic Carbon Fractions: A Meta-Analysis

Abstract

Straw returning can improve soil health, maintain farmland soil fertility, and positively contribute to enhancing soil carbon sequestration. A meta-analysis was conducted on 86 published in the world to quantify the changes of soil organic carbon content and its response to environmental and management factors under the condition of straw returning. The findings revealed that straw returning led to an average increase of 9.12% in soil organic carbon (SOC), with notable increments of 30.34% in particulate organic carbon (POC), 25.53% in microbial biomass carbon (MBC), 21.53% in easily oxidized organic carbon (EOC), 21.39% in dissolved organic carbon (DOC), and 5.71% in mineral-associated organic carbon (MAOC). The effect value of SOC was significantly positively correlated with that of MBC, EOC, POC and MAOC. Under the condition of straw returning, soil organic carbon fractions had different responses to the changes of agronomic practices, soil properties and climate factors. MAOC was the primary contributor to the increase in SOC under straw return, indicating its crucial role in soil carbon sequestration. Key factors influencing changes in organic carbon content included amount of returned straw, mean annual precipitation, years of experimental and initial SOC. Climatic factors emerged as pivotal in driving variations in POC and MAOC following straw return. Therefore, comprehensive consideration of SOC composition, particularly changes in active carbon fractions, is crucial when assessing the ecological benefits of straw return, facilitating a deeper understanding of its mechanisms in promoting soil carbon sequestration and guiding the formulation of scientific farmland management strategies.

Keywords: Soil carbon sequestration, Soil organic carbon fractions, Particulate organic carbon, Mineral-associated organic carbon, Agricultural managements, Climate factors